Process for acetylating cellulose acetate textile materials



Patented May 23, 1939 PROCESS FOR AGETYLA'I'ING ACETATE TEXTILE MATE CELLULOSE mars Henry Dreyfus, London, England No Drawing.

rial No. 1934 2Claims.

This invention relates to improvements in the production of yarns, fabrics and other materials, and is more particularly concerned with processes for the production'of cellulose acetate yarns, fabrics and other materials, and with the new yarns, fabrics and other materials produced thereby.

I have found that the resistance to heat of cellulose acetate yarns, fabrics and other materials may be increased by subjecting the yarns and other materials to acetylation by treatment with diluted acetic anhydride, in the presence of ferric chloride as catalyst. By this means the safe ironing point of thematerials may be increased so that they may be ironed without damage at higher temperatures than are customary in ironing ordinary cellulose acetate artificial silk. In addition, the treatment reduces the moisture regain of the materials and they acquire a greater resistance to. water and have a substantially greater resistance to the delustring action of hot or boiling aqueous liquids or moist steam. At the same time the tenacity and extension of the materials are well maintained. In addition, the af-- flnity of the yarn for dyestuffs in general, and particularly for the dispersed insoluble dyestufls now commonly applied to cellulose acetate, is materially reduced, so that by association of the yams or other materials so treated with yarns or other materials of cellulose acetate or of other organic derivatives of cellulose untreated by the process, diiferential dyeing effects are obtainable, whilst at the same time the dye has an amnity for the whole of the fabric or other material in which the two types of yarn are associated. Thus, for instance, light and dark blue shades can be produced by the immersion in a dyebath containing an SRA blue dyestufl of a fabric containing ordinary acetone-soluble cellulose acetate yarn together with the same yarn which has been subjected to the process ofithe invention.

In addition to increasing the resistance to heat and the resistance to water, the new process has the eifect of changing the solubility characteristics of the yarns or simflar materials. Thus,

for instance, by treating cellulose acetate yarn with acetic anhydride according to the present invention, a yarn may be produced which is insoluble or much less soluble in acetone. Similar changes in the solubility characteristics occur in the treatment of other materials used as starting materials in the treatment of the invention. It is thus possible, according to the invention, to produce yarns or other materials which it is difficult or even impossible to manufacture by a simple spinning process.

In the appended claims, the expression "nonsolvent liquid medium" is to be understood .as meaning a medium which is a non-solvent for the materials being treated throughout the whole of Application September 5, 1935, Se- 39,2 90. In Great Britain September 11,

the reaction, and the expression until products having a reduced solubility in acetone are obtained is to be understood to include the pro- The acetic anhydride is diluted with a diluent which is a non-solvent for the yarn under treatment and is preferably inert thereto, though it may have a swelling action. Good results are obtained with hydrocarbon diluents, for example xylene or other homologues of benzene, tetraand deca-hydronaphthalenes, and kerosene or other higher boiling petroleum hydrocarbons and also ethers, e. g. normal and iso butyl and amyl ethers, carbon tetrachloride and other non-solvent chlorinated hydrocarbons.

The degree of dilution may be adjusted so as to prevent swelling or so as to obtainsome swelling of the yarn. In any case, it should be such as to prevent any solution or incipient solution of the yarn or any fusing together of the filaments, and, further, it may be adjusted to prevent any substantial change in the lustre orquality of the material. A given amount of acetic anhydride may, for example, be dissolved in 'I or 8 or 10 up to 20 times or more of its weight of xylene or other hydrocarbon. The higher dilutions are particularly conducive to avoiding change in the lustre and in quality. The amount of acetic anhydride on the weight of the yarn may vary very considerably, but it is usually sufllcient to use an "amount of anhydride from half to twice the weight of the material, for example a proportion of l-1 times its weight. The proportion may be varied according to the degree of acetylation required and according to the amount of the change in the properties of the material which I it is desiredto bring about.

The reaction may be carried-out under atmospheric pressure, sub-atmospheric pressure, or at pressures in excess of atmospheric, for example pressures of 20 pounds per square inch or more.

The ferric chloride may be employed either alone or in the presence of hydrochloric acid. In general it is found that th'e'presence of hydrochloric'acid accelerates the reaction so that thedesired degree of further acetylationcan be obtained in a shorter time than in the absence of the acid. Preferably hydrochloric acid is introduced into the acetylating medium in the form of co hydrochloric acid, is preferably employed in quite low concentrations.

The actual concentration of catalyst will depend upon the concentration of acetic anhydride and other factors. The catalyst should not be employed in a sufficiently high concentration to bring about reaction between the anhydride employed and any diluent if such reaction is possible. For instance, with certain aromatic hydrocarbons acetic anhydride will react in the presence of ferric chloride if. present in a sufficiently high concentration.

In general the lower the concentration of the acetic anhydride or catalyst, the longer will the time of treatment be. 30 minutes or 1 hour up to five hours or more. The conditions necessitating these longer periods of treatment appear to be conducive to greater uniformity of reaction.

For the purpose of brevity, the term yam has been used, but it will be understood that the yarn may be treated in any suitable form, for example in the formof hanks, or on perforated bobbins in the form of woven or warp-knitted or other knitted fabrics or similar materials.

The most important starting material for the tate yarn. The-starting material may be a yarn produced by the ordinary spinning process, for

example the well-known commercial acetonesoluble cellulose acetate yarn, or it may be a yarn treated by any suitable after-treatment process. for example stretching, shrinking, dyeing or other processes. For example, the yarn subsequent to its manufacture may be-subiected to a stretching treatment designed to increase its tenacity, for example by means of a solution of dioxane or other suitable solvent or in the presence of steam or hot water, as described in U. 8. application S. Nos. 4510 and 4511 filed 1st February 1935. The stretching'treatment may, for example, be such as to extend'the yarn by 200400% or even 1000% or more of its original length. Such yarns have an extremely high tenacity whichis reflected in the final product, treated according to the present invention. Such stretched yarns, or even ordinary artificial silk materials may, if desired, be subjected to a shrinking'treatment to increase their extensibility, for example a shrinking treatment carried out with the aid of latent solvents (see U. 8. application 8. No. 611,240-filed May 13,

1932, now Patent No. 2,058,422, dated October a The reaction between the cellulose acetate yarn and the acetic anhydride may be carried out in any suitable manner, for example as a batch process. Forexample banks may be immersed for the appropriate period in the acetylation mixture, or the mixturemay be pumped or sucked through a perforated bobbin or other 0 package of the yarn.

The following examples are given in order to g It may, for example, be I illustrate the invention, but it is to be understood that they do not limit it in any way. The parts given are by weight in each case.

Example 1 removed, washed first with benzene and then with water and dilute alkali to remove traces of acid and dried.

Example 2 60 parts of acetone-soluble cellulose acetate yarn are treated for about 1 hour at 20-25, C. in a solution consisting of about 1400 partsoi' benzene, 100 parts of aceticanhydride and 2 partsof crystallised ferric chloride. The yarn is then removed, washed as in the preceding example and dried.

Example 3 60 parts of cellulose acetate yarn are treated for about 18 hours at a temperature of 20-25 C.

in a medium consisting of about 800 parts of benzene, 45 parts of acetic anhydride and 1 part of crystallised ferric chloride. The yarn is then removed, washed and dried as in Example 1.

Example 4 60 parts of yarn are treated at a temperature of I 20-25" C. for about 1 hour in a medium consisting of about 800 parts' of benzene, 100 parts of acetic purpose of the present invention. cellulose anhydride, 1 part of crystallised ferric chloride then removed, washed and dried as in Example 1.

The yarn obtained according to each of the preceding examples is chloroform-soluble, has an increased acetyl value, and improved resistance to ironing and to treatment with hot aqueous media and a decreased affinity for the ordinary cellulose acetatedyestuifs.

While the invention has been described above more particularly with reference to yarns, it may also be applied to films, foils and similar materials of cellulose acetate.

What I claim and desire to secure by Letters Fatent is: i

1. Process for the production of improved artificial materials, which comprises subjecting filaments, yarns, threads and similar textile materials having a basis of acetone-soluble cellulose acetate and fabrics containing such materials to acetylation with a non-solvent liquid medium comprising acetic anhydride, an organic diluent and ferric chloride until products having a reduced solubility in acetone are obtained.

2. Process forthe production of improved artiilcial materials, which comprises subjecting filaments, yarns, threads and similar textile materials having'a basis of acetone-soluble cellulose acetate and fabrics containing such materials to acetylation with a non-solvent liquid medium comprising acetic anhydride. an organic diluent,

ferric chloride and hydrogen chloride until products having a reduced solubility in acetone are obtained.

' HENRY DREYFUS. 

